The present invention relates to roller supported rotary drums of the type used for agitating, mixing, heating and/or otherwise handling material (for example, particulate matter). More particularly, the present invention relates to rotary drums having riding rings that are supported on carrying rollers for rotation on a drum axis diverging slightly from a horizontal axis, and which typically require the rollers to be skewed with respect to the riding rings.
The prior art is replete with designs for stands having carrying rollers used to carry rotary drums during rotation about a drum axis that slopes slightly from the horizontal. The slope is necessary to ensure that material being handled by the drum properly travels lengthwise within the drum during the handling process. Typically, a drum will include riding rings extending coaxially around the drum for receiving the required support from the carrying rollers. However, by reason of the slope and the force of gravity, special measures have to be taken to confine axial movement of the drum. Unless restrained, the natural tendency of the drum will be to move axially downhill as the drum rotates.
The primary mechanisms for confining axial movement of a drum are thrust rollers. They act on the riding rings and assist to maintain the rings in a centered position on the carrying rollers. However, they are often not designed to resist the full thrust that a rotary drum and its load may impartxe2x80x94at least not for any significant period of time. To address this limitation, it is commonplace to skew a drum""s carrying rollers in relation to the riding rings in a manner that urges the drum axially uphill as the drum rotates; in effect counteracting the force of gravity. The skew takes place about a skew axis, viz. the axis on a line drawn from the center of rotation of a roller and radially intersecting the drum axis. However, if the skewing is insufficient, a thrust roller may still encounter significant force leading to premature failure. Conversely, if the skewing is excessive, then excessive wear and tear may take place on the riding ring and the carrying roller.
Various mechanisms have been devised for supporting carrying rollers and for adjusting the skew of carrying rollers relative to riding rings. However, they are often quite complex. As well, in the case of many designs, the adjustment of a roller""s skew actually requires a series of adjustment steps; for example, first moving one side of a roller""s support (e.g. to draw it forwardly by a small amount), then moving the other side of the roller""s support (e.g. to push it backwardly by a small amount), then having to repeat such steps until a desired degree of skew rotation has been achieved. The problem is that translational as well as rotational movement may occur unless such adjustments are made with extreme care and precision. With repeated adjustments, serious misalignments with other rollers that should be similarly adjusted can gradually develop. The costly process of realigning an entire installation may then become necessary.
A primary object of the present invention is to provide a new and improved support stand for a rotary drum, the stand including a carrying roller that can be precisely skewed with respect to a riding ring of the drum without allowing translational movement.
A further object of the present invention is provide in association with such a support stand, an adjustment mechanism that permits desired skew adjustments to be easily made.
Yet another object of the present invention is to provide in association with such a support stand a means for easily discerning the amount of skew.
A still further object of the present invention is to provide a rotary drum supported by such support stands, and a method for aligning the stands with respect to the drum.
In a broad aspect of the present invention, there is provided a support stand for supporting an elongated rotary drum for rotation about a longitudinally extending drum axis, the drum including a riding ring extending coaxially around the drum for receiving such support. The stand includes a lower portion extending upwardly from a base to a tilted top which extends in a predefined plane of tilt. A correspondingly tilted upper portion is rotatably mounted atop the lower portion, and is rotatably positionable relative to the lower portion about a skew axis perpendicularly intersecting the predefined plane of tilt at a fixed point. A carrying roller is rotatably mounted on the upper portion for rotation about a roller axis while the ring bears against and rides in rolling contact on the roller with the skew axis substantially radially intersecting the drum axis. As well, the skew axis substantially radially intersects the roller axis.
In a preferred embodiment, the upper portion of the stand is constrained to rotate relative to the lower portion about the skew axis by a center pin extending from the lower portion to the upper portion. The center pin has a center pin axis coinciding with the skew axis. By definition, this arrangement dictates that the skew axis intersects the plane of tilt at a fixed point, that point being the point where the center pin axis likewise intersects the plane of tilt.
Adjustment to a desired position of rotation may be achieved in various ways. An adjustment mechanism that is both rugged and simple comprises a resistance block mounted to the lower portion of the stand and an opposed pair of adjustment bolts, each bolt being threadingly engaged with an associated support bracket mounted to the upper portion of the stand. The bolts are aligned on a common axis that extends tangentially in relation to the skew axis, and the resistance block extends upwardly between the bolts. Each bolt is screwable within its support bracket to bear against the resistance block and thereby urge rotation of the upper portion of the stand relative to the lower portion of the stand about the skew axis. When a desired position of adjustment has been achieved, it may be secured in various ways such as with locking bolts.
In a preferred embodiment, the support stand includes an associated indicator for displaying the amount of rotation about the skew axis of the upper portion of the stand relative to the lower portion of the stand. This amount may be indicated in degrees, minutes, millimeters, or other units of measurement. The particular units of measurement are not critical. Those skilled in the art will understand that a suitable indicator may take various forms ranging from purely mechanical arrangements to electronic or electro-optical position sensing devices coupled to analog or digital readouts. In a preferred embodiment the indicator is a mechanically rugged arrangement comprising a measuring scale visibly marked on one portion of the stand and a pointer directed to the scale from the other portion of the stand. As the upper portion of the stand rotates relative to the lower portion about the skew axis, the pointer moves relative to the scale and the amount of rotation thus can be seen.
Advantageously, first and second pairs of such stands may be used in combination with a rotary drum of the foregoing type, the drum including first and second longitudinally spaced riding rings extending coaxially around the drum. The first pair of stands is associated with the first riding ring and provides support to the drum from opposed sides of the first riding ring. Similarly, the second pair of stands is associated with the second riding ring and provides support to the drum from opposed sides of the second riding ring. Each of the stands has upper and lower portions and a carrying roller as described above, and preferably each includes an indicator as described above for displaying the amount of its rotation about its skew axis. The riding ring associated with each stand bears against and rides in rolling contact on the stand""s roller, the skew axis of the stand substantially radially intersecting both the roller axis and said drum axis.
In another aspect of the present invention, there is provided a method of providing roller support for an elongated rotary drum rotatable about a longitudinally extending drum axis, the drum including first and second longitudinally spaced riding rings extending coaxially around the drum, the method comprising:
(a) for each riding ring, providing a pair of stands for supporting the drum from opposed sides of the ring, each of the stands comprising:
(i) a lower portion extending upwardly from a base to a tilted top lying in a plane of tilt;
(ii) a correspondingly tilted upper portion rotatably mounted atop the lower portion, the upper portion being rotatably positionable relative to the lower portion about a skew axis perpendicularly intersecting the plane of tilt at a fixed point;
(iii) a carrying roller rotatably mounted on said upper portion for rotation about a roller axis, the riding ring associated with the stand bearing against and riding in rolling contact on the roller, the skew axis substantially radially intersecting both the roller axis and the drum axis; and,
(iv) an indicator for indicating the amount of rotation of the upper portion of the stand relative to the lower portion of the stand about the skew axis from an initial datum,
(b) rotating the upper portion of each of the stands about its associated skew axis to a position such that the indicated amount of rotation relative to its lower portion is the same as for all stands.
Normally, the initial datum for a stand will correspond to zero degrees of relative rotation between the upper portion of the stand and the lower portion of the stand. When all four stands are at their initial datum and initially aligned with the drum, then the rollers will be fully squared (viz. in full face contact) with the riding rings. Typically, it is contemplated that such an initial alignment will be performed as a preliminary step on a new installation or, if significant wear and tear has occurred, as an initial step in the process of refurbishing or realigning an old installation. In a preferred embodiment, initial alignment comprises the step of aligning the stands with the drum such that:
(a) the fixed point of intersection between the skew axis and the plane of tilt of the stands define the corners of a rectangle;
(b) the roller axis of a first one of the rollers is axially aligned with the roller axis of a second one of the rollers, and extends parallel to the drum axis; and,
(c) the roller axis of a third one of the rollers is axially aligned with the roller axis of a fourth one of the rollers, and extends parallel to the drum axis.
However, for reasons well understood by those skilled in the art, it often will be necessary for the drum axis of a rotary drum to diverge by a few degrees from true horizontal, the amount of divergence depending on the particular task at hand. It is then unsatisfactory for the rollers to be fully squared with the riding rings. There should be a suitable degree of skew. The present invention is particularly well adapted to enable desirable suitable skew adjustments to be made easily made without otherwise placing stands out of their initial alignment with a drum.
The foregoing and other features and advantages of the present invention will now be described with reference to the drawings.